A BSTRACT Valproic acid (VPA) is a well-established antiseizure medication typically prescribed to maintain serum levels between 50 and 100 μg/mL. This case report presents a 25-year-old male with idiopathic generalized epilepsy who achieved long-term seizure freedom while on significantly subtherapeutic VPA levels. The patient initially maintained seizure control on a 750 mg once-daily regimen, with a measured VPA level of 35 μg/mL and a normal sleep-deprived EEG. Following a reduction to 500 mg daily due to medication-related tremors, seizure control persisted and a repeat EEG remained normal. However, after a further reduction to 250 mg daily, a subsequent EEG revealed new-onset generalized epileptiform discharges. Despite reverting promptly to the prior 500 mg dose, the patient experienced a seizure 3 days later. He remained seizure-free for 1 year following this episode while continuing on the 500 mg dose. This case highlights two important clinical observations: First, seizure freedom can be sustained at subtherapeutic serum VPA levels in certain patients; second, EEG abnormalities may serve as an early biomarker of increased seizure risk following dose adjustments. To our knowledge, such a pattern has not been previously documented. This case emphasizes the utility of EEG in guiding treatment decisions and monitoring subclinical changes in patients with idiopathic generalized epilepsy.
Mazen Basheikh (2026) studied this question.